Olefin polymerization process



Aug. 7, 1956 E. ARUNDALE ET AL 2,758,143

OLEFIN POLYMERIZATION PROCESS Filed Oct. l. 1951 lsTmLATlom 'Zeus-1 C5+POLYMEL OFF GAS 55mm/ATOL ooLErz.

H EAT El HEATEsL Omit-'m om'Amme FEED ErUzLrz Grancia le QH'IOIQ UEQCSIBL'U; @rn/embers Clbborneg United States PatentOfce 2,758,143 Patented Aug. 7, 1956 2,758,143 oLEFm roLYMERrzATIoN rnocnss 'Erving Aruntlale and Byron M. Vanderbilt, Westfield,

N. J., assignors to Esso Research and Engineering Company, a corporation of Delaware The present invention is concerned with an improved process for polymerizing olens. The invention is more particularly concerned with the polymerization of ole'ns wherein the oleiin containing gases are contacted with a particular liquid catalyst comprising an acid f phosphorus. ln accordance with the present invention, an olefin polymerization reaction is carried out in a reactor utilizing phosphoric acid as a catalyst wherein eicient contact and high conversions are obtained by mixing the phosphoric acid with an organic phosphate.

it is well known in the art to use various phosphoric acid type catalysts supported on suitable solid carriers for carrying out polymerization reactions. For instance, it is wel known in the art to treat olefins and olefin-containing streams with various catalysts, as for example, with acids of phosphorus in order to polymerize'the olefins to higher boiling hydrocarbon constituents useful as motor gasoline or chemical raw materials. In general, the feed streams comprise normally gaseous olelins, such as propyl- `ene, butylenes, pentylenes, and mixtures thereof, which are polymerized to hydrocarbon constituents which boil in the range below about 430 F. Although pure oleiilnic ferred to have paranic diluents present in a concentration in the range of from about 20% to 80% by weight in order to reduce the formation of carbonaceous deposits on the catalyst and to provide better temperature control in the catalyst bed.

The phosphoric acid catalyst is usually deposited "on solid carriers, as for example, kieselguhr, diatoma'ceous earth, precipitated silica, silica gel, and the like. In general, these supported catalysts are satisfactory for securing polymerization of the olens in the feed stream. However, there exist certain inherent disadvantages with respect to their use in that their structural strength is lrela- -tively low, resulting in disintegration of the supported catalysts and excessive pressure build-up, thereby necessitating discontinuing the operation. This disintegration of the catalyst is particularly harmful in `a fixed bed type of operation, especially wherein the catalyst is A disposed in relatively long tubular elements vhaving relatively small diameters. In addition, polymerization reactions over such solid catalysts are normally carried out under high pressures of the order of about 500 to 1000 p. s. i.- g. in order to obtain the desired contact between yfeed and catalyst. Eiiicient contact between the feed and catalyst is necessary if high conversions of the olelins' to liquid 'polymer are to be obtained. By employingl the process 'streams may be utilized as feed stocks, it is generally presible to` obtain high olefin conversion and high yields of liquid-polymer at lower pressures as for example at atmospheric pressure.

In accordance with the present invention, an improved polymerization operation is conducted by utilizing a catalyst comprising phosphoric acid in admixture with an organic phosphate. Furthermore, the catalyst is` handled in such a manner that the olefin-containing gases contact the phosphoric acid in an efficient manner. The present invention may be more fully understood by reference to the accompanying figure illustrating one embodiment of the same.

Referring to the drawing, the olen containing feed is passed through line 1 into heater 2 where the temperature is raised to the desired level. The heated feed is removed from the heater zone 2 by means of line 3 and introduced into reactor zone 4. Reactor zone 4 contains the mixture of phosphoric acid and organic phosphate which is heated to the desired polymerization temperature. To increase contact between the feed and catalyst in zone 4, the reactor may be loaded with an inert material auch as porcelain, carbon or the like, or the Catalyst may he agitated by any suitable mixing device, for example, a stirrer. The catalyst mixture in reactor zone 4 is maintained at a temperature suiiicient to cause polymerization of the oletin in the feed but below the normal boiling point of the organic phosphate in the catalyst mixture. Unreacted gas and polymer are removed from zone 4 by means of line 5, usually by distillation, and introduced in cooler 6, thence by line 7 into separator 8. In separator 8 the gas is removed by line 9 while the liquid polymer product is removed by means of line 10 and passed to heater 11. The temperature of the product is raised in heater 11 and introduced into fractionating column 13 by means of line 12,. Hydrocarbons having four carbon atoms in the molecule and lower boiling hydrocarbons are removed overhead from fractionating column 13 by means of line 14. Hydrocarbons having live carbon atoms in the molecule and higher boiling polymers are removed by means of line 15. This Css-|- polymer can be further fractionated to separate material boiling above approximately 430 F. This high boiling material may be recycled to reactor zone 4 if desired. Under certain operating conditions it may be desirable tol bypass cooler 6, separator 8 and heater 11 and introduce the unreacted gas and polymer product which leaves reactor zone 4 by means of line 5 directly into fractionating column 13 by means of line 16.

Another modification of the process would be to contact the heated feed and catalyst while the two are howing concurrently through a heated reactor. The polymer and unconverted gas can then be separated from the catalyst and the latter recycled.

The catalystmixture of the present invention is prepared by mixing phosphoric acid of -105 weight percent concentration with a polar organic compound which isinert. under the polymerization conditions, specifically an organic phosphate. Mixing is carried out quite eiliciently using a high speed agitator although other means, for example, recycle pumping, can be employed in the preparation of the catalyst mixture.

The organic phosphates used in accordance with the present invention comprise the mono, di or tri alkyl or aryl phosphates or mixtures thereof, which possess the following general formula:

wherein R1 represents an alkyl, aryl, aralkyl or alkaryl radical containing l-l8 carbon atoms and wherein R2 and R3 represent alkyl, aryl, aralkyl or alkaryl radicals containing l-l8 carbon atoms or R2 and R3 represent hydrogen atoms. Preferred compounds are the tri-aryl phosphates, wherein R1, R2, and Rs contain from about 6 to 9 carbon atoms in the group. It is also preferred that the aryl groups contain from l to 3 alkyl groups wherein each alkyl group contains from l to 4 carbon atoms in the group.

These organic phosphates may be prepared by any suitable procedure as for example by the reaction of aliphatic alcohols, phenol or alkylated phenols with phosphorous pentoxide or with phosphorous oxychloride followed by hydrolysis. As pointed out for the purpose of this invention, the mono, di or tri aryl phosphates are particularly preferred although other high boiling polar compounds such as the alkyl or aryl phosphites may also be used. A particularly useful catalytic mixture comprises one prepared by reacting phenol or petroleum phosphates phenols with phosphorous oxychloride followed by hydrolysis to form the mono, di or tri phenyl phosphates or a mixture thereof. The by-product hydrogen chloride is separated and the 95-105 phosphoric acid is added. Olen feed is then added to alkylate the aromatic ring, and the catalyst is allowed to come to equilibrium at polymerization temperature.

Other organic phosphates which may be employed in the catalyst mixture include the mono, di or tri esters of phenol, cresol, xylenol, tri methyl phenol, tri tertiary butyl phenol, tri propyl phenol or other alkylated phenols which esters can be prepared as described above or secured from other sources.

The polymerization process of the present invention which employs the improved catalyst is particularly applicable to hydrocarbon feeds containing Ca and C4 oletins by themselves, mixtures thereof, or diluted with C3 and C4 paraflin hydrocarbons, which hydrocarbon mixtures can be produced in thermal or catalytic cracking operations employing petroleum oil feeds. The polymers produced, utilizing the present catalyst possess high octane numbers and can be blended with other refinery products to produce motor or aviation gasolines. These polymers are also valuable as chemical raw materials in that they can be reacted for example with carbon monoxide and hydrogen to form alcohols or with aromatic hydrocarbons a, EXAMPLE I A hydrocarbon feed comprising olens having the following analysis was polymerized in different operations as hereinafter described:

M01 Weight Percent Percent Ethylene 0. 2 0. l1 Propylene 26. 2 22. 14 Propana-. 27. 5 24. 35 Isobutane- 15. 5 18. 10 N butane. 9. 3 10. 86 Isobutylen 6. 5 7. 33 1 butene- 4. 7 5. 30 t 2 butene 5.0 5. 64 e 2 buteue 3. l 4. 17 Butadiene. 0. 1 0. 10 Iso and n. pentan 0.6 0.87 Cl Unsaturates.-- 0. 6 0.84 05.-!- hydrocarbons 0. 1 0. 17

Olen eontent=47% by volume.

This olen feed was passed at atmospheric pressure and at the rate of 0.28 liter (gas) per minute through 502 grams of 97-98 weight percent phosphoric acid in a reactor equipped with a stirrer. Operations were conducted at 239 F. and 293 F. The percent olefin conversion was determined by an Orsat analysis on the product gases.

'The following results were obtained:

ditions as above but the catalyst consisted of 506 grams of 97-98% HsPO4 and 326 grams of tricresyl phosphate. The results of these operations are as follows:

Polymeriza- Percent Olen tion Tempera- Conversion by ture, F. Orsat Analysis operation s. 239 50-52 Operation 4 293 63-66 I V Itis evident that phosphoric acid in combination with the tricresyl phosphate gave about 100% increase in the olen conversion as compared with the use of a phosphoric -acid catalystalone.

EXAMPLE II at such a rate as to insure high olen conversions Which feed rates are usually from about 0.1 to 2.5 volumes of liquid olefin per volume of catalyst mixture per hour.. In order to secure intimate contact between the feed and catalyst mixture, suitable emulsifying or dispersing agents in a concentration between 0.5-5 weight percent based on the catalyst mixture may be added to the catalyst.

The present invention will be more fully understood by the following examples illustrating the same.

n A hydrocarbon mixture similar in composition to that utilized in Example I and comprising hydrocarbons containing 3 and 4 carbon atoms in the molecule and containing 48 volume percent oletins was` passed in' one operation through HaPOt. In other operations the catalyst comprised phosphoric acid and phosphates. The polymerization was carried out in a stirred vessel for v2% hours at a temperature of 239 F. The temperature was then raised to 293 F. for a period of 2 hours. A portion of the polymer distilled overhead and 'the remainder was recovered from the catalyst in the reactor. Orsat analyses were obtained during the course of thei'uns to determine the olefin conversion and the amount Iof off gas was measured in a wet test meter. The results are presented in the following table. Y-

Low pressure plymeri'zatior operations General conditions Cs/C, feed containing 4.8.3 vol. iiercent olens.

Gaseons feed rate: 354.37 l ers/minute. Atmospheric n'essure. Y Y -Rnn length, 9g. hours at (239 F.) then 1 hour and 55 minutes at (293" E).

- Vol. Olettn Weight Weight y, Operation of Temp., on Gas, Conv. Polymer Polymer Total No. Catalyst Cat., F. 1./Min. (by Distllete, y in y' Ott cc. Orsat), g. Reactor, g. Gas, l.

pllt

- l 239 0.344 28-29 A 1 506 gms. 100% mrc. 212 293 0 338 35 36} (T if.; vv$11.0 94.85

ot'a o y. 23. II 379.0 gms. of mixture containing 64.3 wt. percent 100% 284 239 0.336 25. 5-26 18 2 s 0 92 02 H3PO4+35-7 wt. percent of a high boiling petroleum oil 293 0.331 32-34. 5 (contains 24e gms. of HQPQQ. (Total Po y. 18.2 g.) III 413 gms. of mlxture contaunng 58 wt. percent 100 percent 280 239 0.267 57-59 42 5 19 1 74 o POi-i-f percent tri xylenyl phosphate (contains 293 0. 262 60-61 (T l'P gms. 3 4 ota o y. 61.6 g. IV 829.4 gms. of mixture containing 58 wt. percent 100% 239 0.256 70-73 562 27 2 42 4 70 6 HsPOl-i-42 wt. percent tri xylenly phosphate (contains 293 0. 246 69. 5-72 480 gms. HaPOi). (Total Po y. 69.6 g.)

It will be noticed that the use of 100% HaPO4 per se as a catalyst at atmospheric pressure and temperatures of 239 F. and 293 F. results in low olefin conversions (Z8-36%) and low polymer yields. In operation II the use of an equivalent volume of total catalyst but in the form of a mixture with inert oil results in still lower conversions and polymer yields. On the other hand, in operation III, when substituting trixylenyl phosphate, the olen conversion (S7-61%) and yield of liquid polymer are at least double those which can be realized, under comparable operating conditions, with HaPO4 by itself as the catalyst. In operation IV, by doubling the volume of the HsPOr, trixylenyl phosphate catalyst resulted in a further increase in olefin conversion (70-73%) and liquid polymer yield.

While the applicants do not wish to be restricted as to theory of operation, it is believed the superiority of the phosphoric acid-polar organic compound mixtures over phosphoric acid alone as a polymerization catalyst is due to several factors. The phosphoric acid forms a good dispersion or emulsion in the organic phosphate which presents a greater surface area of the acid catalyst to the olefin feed gas and thereby improves the contact. The triaryl phosphates react with the 100% phosphoric acid to form a mixture of monoand di-aryl acid phosphates which mixture with phosphoric acid is a more active polymerization catalyst than phosphoric acid alone. The phosphate portion of the mono, di or tri aryl phosphate molecule is soluble in the phosphoric acid and the aryl portion of the molecule compatible with the feed thereby effecting improved contact between the feed and acid catalyst. This is apparently the case since solubility determinations have indicated that both 100% H3PO4 and hydrocarbons have an appreciable solubility in the trixylenyl phosphate. For this reason, phosphoric acid can be dissolved in such a mutual solvent as an aryl phosphate and the feed passed through the homogeneous solution at an elevated temperature taking the polymer off overhead as it is formed.

The concentration of the organic phosphate in the catalyst mixture may vary appreciably depending upon operating conditions, the particular organic phosphate utilized, and upon other variables. However, in general, it is preferred to use from to 70% by weight of the organic phosphate in conjunction with from about 30% to 80% by weight of the phosphoric acid. A preferred concentration of the organic phosphate on this basis is from about 40% to 60% by weight.

What is claimed is:

l. An improved process for polymerizing olens which comprises contacting the oletins under polymerization conditions with a mixture of a inorganic acid of phosphorus and a hydrocarbon ester of phosphoric acid containing at least one aromatic hydrocarbon substituent group.

2. Process as defined by claim 1 wherein said hydrocarbon ester has the following general formula:

wherein R1, R2, and R3 are selected from the group consisting of hydrocarbon radicals having from 1 to 18 carbon atoms in the radical and hydrogen and at least one of the R groups is an aryl radical.

3. Process for polymerizing olefins utilizing a phosphoric acid which comprises contacting the olefins with said phosphoric acid in admixture with an aryl hydrocarbon phosphate selected from the group consisting of mono, di, and tri aryl phosphates, wherein the aryl group contains from 6 to 9 carbon atoms in the group.

4. A process for polymerizing C3-C4 oletins which comprises contacting said olens with a catalyst comprising a mixture of -105% phosphoric acid and a hydrocarbon phosphate ester containing at least one aryl group having from 6 to 9 carbon atoms at a temperature between about 240-450 F. and at a pressure from atmospheric to 500 p. s. i. g. and removing the polymer as it is formed.

5. Process as defined by claim 4 wherein said phosphate comprises trixylenyl phosphate.

6. Process as defined by claim 4 wherein said phosphate comprises tricresyl phosphate.

7. Pro-cess as defined by claim 4 wherein said catalyst contains in the range of about 20 to 70% by weight, based on the total composition, of said phosphate ester.

8. As an improved catalyst composition, a mixture of a phosphoric acid and from 20 to 70% a hydrocarbon ester of an inorganic acid of phosphorus containing at least one aromatic hydrocarbon substituent group.

9. A composition as defined in claim 8 wherein said hydrocarbon ester has the following general formula:

wherein R1, R2, and R3 are selected from the group consisting of hydrocarbon radicals having from 1 to 18 carbon atoms in the radical and hydrogen, and at least one ot' said R groups is an aryl radical.

10. As an improved catalyst composition, an emulsion formed by mixing a phosphoric acid and a hydrocarbon ester of an inorganic phosphoric acid, said ester containing at least one aryl radical having in the range of 6 to 18 carbon atoms, said composition containing from about 2O to about 70% of said ester.

11. A composition as defined by claim 10, wherein each aryl radical has in the range of 6 to 9 carbon atoms.

12. A composition as dened by claim 11 wherein said aryl groups are alkaryl groups.

13. A composition as dened by claim 12 wherein said acid is 95 to 105% phosphoric acid.

14. A composition as in claim 13 wherein said aryl phosphate is trixylenyl phosphate.

15. A composition as in claim 13 wherein said aryl phosphate is tricresyl phosphate.

v 16. A process 'for polymerizing normally gaseous oleins to form liquid polymers which comprises contacting said olefins at polymerizing conditions with a catalyst emulsion consisting of 95105% phosphoric acid and tricresyl phosphate, said phosphate being present in an amount in the range of about 20 to 70% by weight based on the total emulsion.

References Cited in the ile ofv this patent A y UNITED STATES PATENTS Linn May 17, 1949 2,592,428 Kemp et al. Apr. 8, 1952 2,614,136 Koienbach et al Oct. 14, 11952 FOREIGN PATENTS 340,513 Great Britain Dec. 22, 1930 450,592 Great Britain July 20, 1936 790,945 France Nov. 29, 1935 

1. AN IMPROVED PROCESS FOR POLYMERIZING OLEFINS WHICH COMPRISES CONTACTING THE OLEFINS UNDER POLYMERIZATION CONDITIONS WITH A MIXTURE OF A INORGANIC ACID OF PHOSPHORUS AND A HYDROCARBON ESTER OF PHOSPHORIC ACID CONTAINING AT LEAST ONE AROMATIC HYDROCARBON SUBSTUTUENT GROUP. 